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Re: [TCML] Salient Pole Query



Phil -
 
Your motor is designed for 50Hz service, and has a synchronous no-load speed (at 50Hz) of 1500 RPM. It is a 4-pole motor, which means it needs to have 4 flats machined into the rotor to achieve salient-pole operation. 
 
Some people have created the flats on the rotor with files, grinders, belt sanders, etc but all of these "machining" methods are crude and will undoubtably leave the rotor unbalanced, which will eventually cause problems with vibration and runout of the RSG disk, premature bearing wear, etc.
 
The only satisfactory method of machining the flats is to use a milling machine. If you don't have access to one, find a machinist who can do the work for you. It takes well under an hour, and rotor balance is generally satisfactory as-machined. 
 
First determine the width of the required flat, position the rotor in the milling machine vise, and machine flat #1. If the mill has a Z-axis encoder, record the depth of the cut. If no Z-axis encoder, set up a dial indicator so you can measure the depth of the cut.
 
Turn the rotor 180 degrees, positioning flat #1 against a set of parallels located under the rotor, between the vise jaws. This ensures that the second flat is exactly 180 degrees from the first flat. Again, monitor the total depth of cut, matching the first cut.
 
Next, turn the rotor 90 degrees so the flats you just created are against the faces of the vise jaws, and machine flat #3. Indexing the rotor on the two flats assures that the third flat is exactly 90 degrees to flats #1 and #2. Again, carefully monitor the depth of cut. Finally, flip the rotor in the vise so the last surface to be machined is oriented up, and cut the last flat, matching the total depth of cut
 
It takes only slightly longer to do the machining than it does to describe the process.
 
Done carefully, the vibration of the converted motor is no worse the the original motor was.
 
Regards,
Herr Zapp

--- On Mon, 12/1/08, Phil Tuck <follies@xxxxxxxxxxxx> wrote:

From: Phil Tuck <follies@xxxxxxxxxxxx>
Subject: [TCML] Salient Pole Query
To: tesla@xxxxxxxxxx
Date: Monday, December 1, 2008, 2:16 PM

Hello.

I am thinking of a SRSG as my next 'project' and have looked into
salient
pole motors converted from induction motors. My own motor has very little
info on the label so I am unsure as to its suitability.

The website at 

http://evolve000.4hv.org/tesla/tc2srsg.html

describes the work involved and my motor does indeed look similar, although
my armature has individual segments on its surface, whilst the webpage
example has a plainer looking armature.

 

Could someone look at my temporary page at 

http://homepage.ntlworld.com/follies/temp/temp.html

and let me know if my motor is indeed suitable. 

My motor though is rated at 1425 rpm, while the web article only describes
1750 (needs 4 flats) & 3450 (needs 2 flats) rpm motors however.

I am UK based at 50 cycles is that the reason for the difference?

 

Regards

Phil

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